Observers, or listeners, may be employed within a piece of software to monitor events that occur within the software and take necessary actions in light of the occurring events. In order to detect desired events, listeners may be registered to an object, or subject, through an application programming interface in order to monitor changes in object features. Listeners may implement an interface prescribed by the object in order to receive notifications about the occurrence of certain events.
Domain modeling describes a means for understanding real world entities and the relationships between those entities. Domain modeling may provide various approaches related to solving a specific problem. A domain model may include a network of model objects that represent various entities within the domain model. A model object may define certain application programming interfaces for registering and unregistering listeners.